Study On Resistive Switching Characterization And Mechanism Based On LiFePO₄ Thin Film

Resistive random access memory?RRAM?has caught widly attention for its high density,super speed,simple structure and low power cost in recent years.The main switching mechanism of the RRAM based on metal oxide is attributed to the recombination of oxygen ion and oxygen vacancy under electric field.Similar to the oxygen ion migration,the working mechanism of lithium ion battery is controlling reversible extracting and insertion of lithium ion,and the process of which may realize reversible resistive switching.Therefore,in this paper,we applied LiFePO₄,the performance of which is relative excellent,to the research of RRAM,and have studied the performance and switching mechanism.We apply the layered graphite,the capacity of storing Li⁺ of which is outstanding,to be the substrate and bottom electrode.We use PLD technology to the preparation of LiFePO₄ at600? under the Ar atmosphere,and apply Au to be top electrode.We study the resistive switching performance of Au/Li FePO4/C memory cell firstly.The result of I-V characteristics shows that the devices have superior and stable bipolar resistive switching capacity,what's more,forming free feature,low write and erase voltage?approximately ±1.5V?,relative high on/off ratio?>102?,excellent retention characteristic?>104s?,and fast switching speed?<50ns?.Further research shows that the devices reveal multilevel resistive switching effect through adjusting the compliance current and reset voltage.The results of different thickness of the dielectric layer,different bottom electrode materials,and multilevel resistive switching effect indicate that the resistive switching phenomenon is relevant to the lithium ion content in the film.In addition,the resistance-temperature dependence in different resistance states,secondary ion mass spectroscopy?SIMS?and Raman spectrum convincingly demonstrate the lithium ion indeed migrate under electric field.In the paper,we assume the resistive switching model based on above experiments: the devices realize reversible resistive switching through controlling lithium ion concentration under electric field.As the positive voltage applied on the top electrode,the lithium ion?Li⁺?would migrate to the bottom electrode,and stored in the layered graphite.The RRAM realizes switching from HRS to LRS because of the formation of channel which lithium ion concentration is relatively low.Conversely,the lithium ion would migrate back to the LiFePO₄ film as infliction of the reversed voltage,and the device realizes the transformation from LRS to HRS.In summary,in this paper,we apply PLD technology to prepare the Au/LiFePO₄/C devices,which show excellent resistive switching characteristic,and study the switching mechanism.The research of this paper demonstrates that the RRAM based on LiFePO₄ materials have a outstanding application prospect.